lathe - Automatic lathes Mt u2 part_3
- 1. Automatic lathes Aditya College of Engineering. Madanapalle By: Amar Gandhi Faculty ,Dept. of Mechanical Engineering
- 2. AUTOMATS Machines capable of handling the work pieces, as well as perform metal cutting operations automatically are known as Automatic machines or Automats. Automatic machines play a vital role in increasing the rate of production and have been in use for production of machine components. Various devices like cams, stops, trip dogs , mechanism etc are used for controlling operations. As automatic machines have fully automatic cycle, the intial setting on these machines must be done very carefully. All that operator has to do into renew bar stock, when it is exhausted and inspect the work pieces at regular intervals of time during the operation.
- 3. The various methods used for achieving automation in machine tools are:- 1. The feeding arrangements, like feed hopers and strip feed rolls. 2. Incorporation of cams and mechanical movements. 3. Special purpose machines designed specially for these Operations ie. Gear shaper, Gear hobber, Broaching machine etc. 4. Transfer machine system. In this system machines are made by a collection of assembled machining units and designed to perform a concerned sequence of operation. Ex. Unit Built Machines( U.B.M)
- 4. Classification of Automats 1. According to type of work materials used:- a. Bar stock machines b. Chucking machines 2. According to No. of spindles:- a. Single spindle machines b. Multi-spindle machines. 3. According to position of spindles:- a. Horizontal spindle type b. Vertical type spindle 4. According to the use:- a. General purpose machine b. Single purpose machine 5. According to feed control:- a. single cam shaft rotating at constant speeds b. single cam shaft rotating at two speeds c. Two cam shafts.
- 5. Single spindle machines These machines produce short w/p of a simple form by means of cross sliding tools. Machines are simple in design. Headstock with spindle is mounted on bed. 2 cross slides are located on bed at front end of spindle. Cams on cam shaft actuates movements of cross slide through system of levers. Some of the single spindle lathes are: 1. Automatic cutting off machine 2. Automatic Screw Cutting machine 3 Swiss type Automatic Screw machine
- 7. Operation: The required length of work is fed out with a cam mechanism, up to Bar stop which is automatically advanced in line with spindle axis at each end of cycle. Stock is held in collet chuck of rotating spindle. Machining is done by tools that are held in slides operating only in cross wise direction Typical simple parts ( 3 to 20 mm dia.) machined on such machines.
- 8. MULTI-SPINDLE AUTOMATS These are fastest type of production machines and are made in a variety of models with 2,4,5,6,8 spindles. In contrast with single spindle m/c where one turret face at a time is working on one spindle, in multi spindle m/c all turret faces works on all spindles at same time. Production capacity is higher, machining accuracy is lower compared to single spindle. Because of longer set up time, increased tooling cost these machines are less economical than other on short runs, more economical for longer runs.
- 9. The Multi-spindle automatic lathes are classified as follows:- 1. According to type of work piece used: a. Bar type machine b. Chuck type machine 2. According to arrangement of spindles; a. Horizontal spindle type b. Vertical spindle type 3. According to principle of operation: a. Parallel action type b. Progressive action type
- 10. Multi- spindle automatic lathe
- 11. SINGLE SPINDLE AUTOMATS 1. Automatic Cutting Off Machine: These machines produce short w/p’s of simple form by means of cross sliding tools. Machines are simple in design. Head stock with spindle is mounted on bed. 2 cross slides are located on bed at front end of spindle. CAMS on cam shaft actuate movements of cross slide through system of levers.
- 13. Operation: The required length of work(stock) is fed out with a cam mechanism, up to stock stop which is automatically advanced in line with spindle axis at each end of cycle. Stock is held in collet chuck of rotating spindle. Machining is done by tools that are held in slides operating only in cross wise direction. Typical simple parts (3 to 20 mm diameter) machined on such a machine is shown in fig.
- 14. 2. Automatic Screw Cutting machine This machine is also called Turret type automatic Screw cutting machine , because it has a Turret head. This machine is used for producing small screws of all types. Complex shapes on external and internal surface of parts can be produced. Parts are produced from bar stock or from separat blanks. The size of parts varies from 12.5 mm to 60 mm in diameter. The different operations performed on this machine are Centering, Turning, cylindrical, Tapered and formed surfaces, threading, Drilling, Boring, Reaming, Spot facing, Knurling, cutting off.
- 16. Operation: Head stock is stationary & houses thespindle. Bar stock is held in collet chuck & advanced after each piece is finished & cutoff. All movements of machine units are actuated by cams mounted on camshaft. Bar stock is pushed through stock tube in a bracket & its leading end is clamped in rotating spindle by means of collet chuck. By stock feeding mechanism bar is fed out for next part. Machining of central hole is done by tools that are mounted on turret slide. Parting off/ Cutting off, form tools are mounted on cross slide. At end of each cut turret slide is with drawn automatically & indexed to bring next tool to position.
- 17. 3. Swiss Type Automatic lathes or Sliding Head Automatic lathes This machine was designed and developed in Switzerland. It is also called Swiss Auto Lathe. This machine is also known as Sliding Head Screw machine or Movable Head stock machine. This machine is used for machining long accurate parts of small diameters say 2 to 25 mm. These parts are produced from Bar stock. The machine has the following features:- 1. A Sliding head stock 2. A Tool bracket having 2 to 5 tool slides 3. A special attachment called Feed base. 4. A Cam shaft
- 19. Operation: The bar stock is held in the rotating spindle by a Collet. Head stock slides along the bed ways with the rotating bar stock. Head stock movements gives longitudinal feed to the work. All the tools in tool slides removes material from work piece at same time. The tool in the Feed base may also do operations like Drilling After the work piece is machined, head stock slides back to the original position. one revolution of the Cam shaft produces one component. Most of the turning and forming operations are done by the tools held on the Front and Rear tool slides. The vertical tool slides are mainly used for Under cutting, Chamfering, knurling and Cutting off..
- 20. Multi- spindle automatic lathe These machines are improved type of single spindle automats. These are having 2 to 8 spindles But 4 & 6 spindles are generally used. operations carried out simultaneously in all the spindles, therefore rate of production is very high. According to principle of operation: a. Parallel action type b. Progressive action type
- 21. MULTI-SPINDLE AUTOMATS 1. Parallel Action Multi-spindle Machine This is also called multi spindle flow machine. Same operation is done in all the spindles in the machine. The work piece is finished in each spindle in one working cycle. The rate of production is very high. This machine is suitable for Production of small parts of simple shape from bar stock. The machine has frame with headstock. In the headstock horizontal spindles are situated. All the working motion and idle motion of all the spindles are obtained from a cam mounted on shaft. If anything goes wrong in one spindle station, the production in that particular station only affected.
- 24. 2. Progressive Action Multi-spindle Machine In this type, the work pieces are machined in stages. The headstock is mounted on left end of base of machine. The headstock has spindle carrier. Working spindles are mounted in spindle carrier. Work pieces are held in collets in the spindles. Bar stock is fed through each spindle from the rear. Cross slides are mounted in a frame above the face of spindle carrier. These tool slides carry forming, facing, chamfering and cutting off tools.
- 26. These cross slides travel radially inward for cutting operation. The slide movement is controlled by cam in cam shaft. The main tool slide is situated in front of spindle carrier. Here also, number of tool slide around its periphery. There is one tool slide corresponding to each spindle. Tool moves towards the spindle while machining. Operations like straight turning, boring and threading are done by tools mounted on these tool slides. The spindle carrier indexes on its own axis by 600 at the end of tool return. As the spindle carries indexes, work moves from station to station.
- 27. - In first station bar is fed. In every station, different operations are done progressively. A finished component is obtained each time, the spindle carrier indexes. Rate of production moderate. If one station goes wrong, production completely affects.